Horticulture & Plant Health

Plant Pest information

Oak Processionary processionea Linnaeus What is it?

Thaumetopea processionea, commonly known as the processionary moth (OPM) is a native species of central and southern Europe. The larvae () feed on the foliage of many species of , including English, Sessile and Turkey oaks (Quercus robur, Q.petraea and Q.cerris). , , , sweet chestnut and are also reported to be attacked, although mainly when Fig. 1 Adult OPM Moth (DEFRA) growing next to severely defoliated oaks. Oak processionary moth is widely distributed in central and southern Europe but the range of this moth has been expanding northwards possibly in response to climate change. It is now firmly established in northern France and the Netherlands, and has been reported from southern . Since 2006, colonies of larvae have been found in parts of London. It has neverbeen found in Ireland.

What should we be worried about it?

The caterpillars of this moth can cause severe defoliation of oak trees and if oak trees have been heavily defoliated the caterpillars have been known to move to other non-oak hosts such as Hornbeam, hazel, beech, sweet chestnut and birch.

This moth also poses a risk for human health because the body of the is adorned with numerous irritating hairs.

How do we recognise the pest?

Fig. 2 OPM caterpillar (DEFRA) The caterpillars are usually found from April to June. The newly hatched larvae have a uniformly brown body and dark head. As they grow they lighten in colour so that, by the time they are mature they have a grey body and dark head. These older larvae have a single dark stripe running down the middle of the back and a whitish line along each side. Clumps of extremely long white hairs arise from reddish orange warts (pinacula) along the length of the body. Less easy to see are the many thousands of short hairs that also cover the larvae. It is these short hairs that contain an irritant toxin. The larvae feed together in groups and, when not feeding, they congregate in communal nests made of white silk webbing spun up under a branch or on the trunk. The larvae typically follow one another head to-tail in long ‘processions’ to and from the nest and from one feeding position to another, which gives rise to the common name.

Human Health Risks

Hairs present on the larger larvae contain an urticating defensive toxin, thaumetopoein, a chemical potentially harmful to humans. Contact with the hairs can provoke allergic reactions manifested as skin rashes, conjunctivitis and respiratory problems such as pharyngitis and asthma. Health problems can occur even if the larvae Fig. 2 Rash from contact with hairs are not handled as the hairs break off readily and are dispersed in air (DEFRA) currents. Abandoned nests contain shed skins, pupal cases and vast numbers of detached hairs and should be treated with extreme caution. Do Not: • touch or approach nests or caterpillars • let children touch or approach nests or caterpillars • let touch or approach nests or caterpillars • try removing nests or caterpillars yourself – call an expert

Do: • teach children not to touch or approach the nests or caterpillars • seek medical advice if you think you or someone you care for has been seriously affected • see a vet if you think your pet or livestock has been seriously affected Fig. 3 OPM caterpillar (DEFRA) • call in a pest control expert to remove infestations in your own trees • report sightings to the Department of Agriculture, Food and the Marine.

Fig. 4 OPM nest (DEFERA)

In 2014 Ireland was granted Protected Zone status for this pest under Take action in the European Plant Health Directive. Any suspected sightings of this pest the event of should be reported to your local plant health inspector or the Division Headquarters at the number below. Please note it is unlikely to be found suspect cases on any other tree than oak and the other hosts mentioned in the text and the nests are almost always found on trunks or branches and not interwoven between the leaves.

Horticulture and Plant Health Division, Department of Agriculture, Food and the Marine, Backweston Campus, Celbridge Co. Kildare Phone: 01 5058885 Fax: 01 6275991 Email: [email protected] Horticulture & Plant Health

Achieving the highest possible standards of Plant Health, Food Safety and promoting the development of an efficient primary horticultural sector

An Roinn Talamhaíochta, Bia agus Mara Department of Agriculture, Food and the Marine Backweston Campus Celbridge Co. Kildare

Phone: 01 5058885 Fax: 01 6275991 Email: [email protected]